It has long been known that the basis of operation of various sewing machine mechanisms relies on the creation and sustenance of an adequate lubrication wedge between the rotating surfaces of the operating parts. Thus, a multitude of various lubrication systems have been devised to accomplish this end. The increased speed of today's machines, however, has led to problems relative to the lubrication and service life of various sewing machine components including eccentric bearings which are used to drive various gear trains.
The requirements for the lubrication of an eccentric bearing are severely exacting. Too little lubricant delivery at high speed operating conditions can cause the eccentric to over heat and seize. An excessive delivery of lubricant, on the other hand, may hinder its operation.
It is known in the art to direct lubricant through an axial bore in a drive shaft and through radial bores therefrom to the bearing surface. U.S. Pat. No. 3,418,955 granted Dec. 31, 1968 to J. G. Attwood, et al is one example of such means. This measure, however, has proven not sufficient by itself for reducing the increased friction in sliding or friction bearings wherein the machines are operated at higher speeds. As a result, many of the eccentric bearings in high speed sewing machines are today provided with roller or anti-friction bearings. The drawback with this solution is the undesirable noise which results.